Even in patients whose last negative colonoscopy was more than 10 years before, advanced adenomas were rare, Dr. Hermann Brenner and his colleagues reported.
The finding suggests that “extension of screening intervals, which could strongly enhance acceptance and cost-effectiveness of endoscopy-based screening and reduce its discomfort, might be achieved while maintaining high levels of safety,” they wrote (Gastroenterology 2010 March [doi:10.1053/j.gastro.2009.10.054
A previous case-control study, also led by Dr. Brenner of the division of clinical epidemiology and aging research at the German Cancer Research Center in Heidelberg, Germany, found a significant 67% reduction in risk of colorectal cancer among people who had a negative colonoscopy between 10 and 19 years prior, and a nonsignificant 54% reduction in risk among people whose negative screening was 20 or more years before (Gut 2006;55:1145-50). However, that study had been restricted to colorectal cancer and had not looked at adenoma rates.
“The current study provides evidence that a similarly very low risk is also seen if advanced colorectal adenomas are included in a combined end point of advanced neoplasms,” the authors wrote. “Taken together, these patterns support suggestions that a very low risk of clinically relevant colorectal neoplasms prevails far beyond 5 or 10 years after a negative colonoscopy, the most commonly recommended intervals for endoscopic screening examination of the large bowel.”
In the current study, Dr. Brenner and his colleagues looked at 2,701 patients who had never had a colonoscopy, as well as 533 patients with a history of one or more prior negative colonoscopies. “Three-quarters of participants with previous negative colonoscopies had just one previous colonoscopy, almost 20% had two previous colonoscopies, and only 5% had three or more previous colonoscopies,” the authors wrote.
All of the participants were age 55 or older. In the colonoscopy-naive group, the mean age was 63.8 years and about half of the participants were female. In the group with a history of negative colonoscopy, there were a slightly greater proportion of women (57.6%) and the mean age was slightly older (65.1 years). The mean time since last colonoscopy was 11.9 years.
“Among participants without previous colonoscopy, the most advanced finding at screening colonoscopy was colorectal cancer in 41 cases (1.5%), advanced adenoma in 267 cases (9.9%), and other adenoma in 494 cases (18.3%),” the authors wrote.
In patients with a previous negative colonoscopy, no patients had colorectal cancer, and 25 (4.7%) had advanced neoplasm.
“These numbers are far and significantly below the numbers that would have been expected based on the age- and sex-specific prevalences in participants undergoing first-time colonoscopy,” wrote the authors—8.4 cases for colorectal cancer and 59.4 for advanced neoplasm, in a cohort of this size.
Additionally, “among those with a negative colonoscopy more than 15 years ago, the prevalence was still more than 40% lower than among those with no previous colonoscopy, even though this difference failed to reach statistical significance,” they added.
Disclosures: The authors reported no conflicts of interest related to the study, funded by a grant from the Central Research Institute of Ambulatory Health Care in Berlin, Germany.